In continuation of our past research interests, we intend to investigate a number of connected problems on the relation between the structure and function of pancreatic deoxyribonuclease (DNase). This research promises to lead to a substantial clarification of the mechanism by which the two specificity structures of DNase give single and double strand breaks in DNA. This work should extend usefulness of the enzyme as a tool in nucleic acid research. Major problems to be investigated include the following: 1. Chemical Modification of the active site, including the use of amino acid specific reagents. Chemical modification also will be used to characterize the metal binding sites on DNase and to distinguish between a one or a two active site mechanism for double strand scission. 2. Metal ion Requirements of DNase, including the role of Ca2 ion in substrate binding and the essential role of Mg2 ion in catalysis. 3. Mechanism of double strand scission, including the conditions at which it occurs and the characterization of the kinds of ends left at a double strand break and the stickiness of these ends. 4. Physical Studies on DNase, including the rate of conformational changes, the X-ray crystallography of DNase, and the characterization of the coordination structure in Co2 ion, Cu3 ion, and Mn2 ion complexes with DNase. BIBLIOGRAPHIC REFERENCES: P.A. Price, "The Essential Role of Ca2 ion in the Activity of Rovine Pancreatic Deoxyribonuclease," J. Biol. Chem. (1975) 250: 1981-1986. A Douvas and P.A. Price, "Some Effects of Calcium and Magnesium ions on the Activity of Bovine Pancreatic Deoxyribonuclease," Biochem. Biophys. Acta (1975) 395: 201-212.